Ultra wideband (UWB) electromagnetic signals can be used in a wide range of applications. Such signals typically comprise very short pulses presented at low duty cycles. As such, UWB signals can be advantageous, especially in applications in which it is desirable to maintain low average power levels. UWB radar can be used to measure the locations of objects at short ranges or to obtain images of objects. UWB devices can also be used for wireless communications, particularly for short-range and high rate data transmission.
UWB electromagnetic signals may have frequencies in the range of a few hundred MHz to about 12 GHz. In typical applications, UWB signals are used in the band from 3.1 GHz to 10.6 GHz. In particular UWB devices the frequencies of electromagnetic signals may be limited to particular regions of the spectrum to comply with applicable regulatory requirements. For example, some devices may be made to operate in a sub-band of the UWB spectrum that occupies the UWB spectrum in the range of 3.6 GHz to 4.6 GHz. In the United States this sub-band has been allocated by the Federal Communications Commission (FCC) for use by certain UWB devices.
While various UWB devices exist, there remains a need for practical and cost effective solutions for use in UWB systems. For example, there exists a need for practical and cost-effective antennas and antenna systems that can be used to transmit and/or receive UWB signals in various contexts. There is a particular need for such antennas that are compact and provide directional radiation patterns. There is also a need for practical and cost-effective UWB radar transceiver circuits.
Another field in which practical and cost-effective technology is required is the field of monitoring the vital signs of people or animals. For example, it would be beneficial to provide a system capable of monitoring the heart and breathing rates of patients in care facilities and in peoples' homes. While such systems exist, most have various disadvantages. For example, some require that electrodes or other devices be attached to each person being monitored, other systems are prohibitively expensive or insufficiently versatile, other systems are only capable of monitoring one vital sign, such as heart rate.
The prior art includes:                Newham, U.S. Pat. No. 5,471,198 and Edwards, U.S. Pat. No. 6,788,206 which disclose systems for monitoring for the presence of persons using reflected energy.        Richards et al., U.S. Pat. No. 6,900,732 which discloses a system for monitoring assets, objects, persons or animals using UWB signals.        Richards et al., U.S. Pat. No. 6,466,125 which discloses a system, electronic monitor and method that utilize impulse radio technology to alert medical personnel when a patient needs medical assistance.        Richards et al., U.S. Pat. No. 6,504,483 which discloses the use of impulse radio to track a position of a horse as it moves around a race track and/or to enable people to monitor one or more vital signs of the moving horse. The patent discloses that the technology may also work with other animals, such as dogs, and with people.        Hall et al., U.S. Pat. No. 6,661,342 which discloses the use of impulse radio to track moving athletes and to provide secure communication with athletes.        Nowogrodzki et al., U.S. Pat. No. 4,513,748 which discloses a heart rate monitor that utilizes two RF signals.        Bloice, U.S. Pat. No. 3,796,208 which discloses a system for monitoring movements of a patient using a microwave radar unit.        Lye et al, WO 2004/047630 which discloses a system that uses UWB signals to transmit information regarding the health condition of a user.        Tupin et al. U.S. 2004/0249258 which discloses the use of UWB radar for imaging and acquiring physiological data.        McEwan, U.S. Pat. No. 5,361,070, which discloses a UWB radar motion sensor.        Edwards, U.S. Pat. No. 6,788,206 discloses a patient monitoring system.        